I didn't realize succession was in place prior to being sworn in. He's not technically president so I would not have thought that was the case.
It's not due to him, it's the general order, no matter who is president. This is how it currently breaks down.
1 Vice President Joe Biden (D)
2 Speaker of the House of Representatives Paul Ryan (R)
3 President pro tempore of the Senate Orrin Hatch (R)
4 Secretary of State John Kerry (D)
5 Secretary of the Treasury Jack Lew (D)
6 Secretary of Defense Ash Carter (D)
7 Attorney General Loretta Lynch (D)
Secretary of the Interior Sally Jewell (D)[a]
8 Secretary of Agriculture Tom Vilsack (D)
9 Secretary of Commerce Penny Pritzker (D)
10 Secretary of Labor Tom Perez (D)
11 Secretary of Health and Human Services Sylvia Mathews Burwell (D)
12 Secretary of Housing and Urban Development Julián Castro (D)
13 Secretary of Transportation Anthony Foxx (D)
14 Secretary of Energy Ernest Moniz (D)
15 Secretary of Education John King (D)
16 Secretary of Veterans Affairs Bob McDonald (R)
17 Secretary of Homeland Security Jeh Johnson (D)
Sally Jewell was born in London and thus isn't a natural born citizen, so she isn't eligible for the office, which is why she's skipped.